1. Field of the Invention
The invention generally relates to electronics. In particular, the invention relates to handling DC offsets in amplifiers.
2. Description of the Related Art
Typical analog amplifiers have a saturating input-output relationship, as illustrated in FIG. 1. Linear signal processing typically uses operation in the linear part of the curve—at smaller inputs levels. Large input signals, or high-gain can result in output saturation. If the ac portion of the desired input signal is sufficiently small, but the dc portion is relatively large, then with sufficient gain, the output will be saturated.
In a direct conversion radio, a schematic of an example of which is illustrated in FIG. 2, there are several sources of these undesirable dc offsets, such as: amplifier input-referred DC offsets due to device mismatch; local oscillator self-mixing; 2nd order distortions; and 1/f transistor noise in amplifiers.